package com.imu.purse.config;

import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;  
  
/** 
 *  
 *  
 * google身份验证器，java服务端实现 
 *  
 * @author yangbo 
 *  
 * @version 创建时间：2017年8月14日 上午10:10:02 
 * 
 *  
 */  
public class GoogleAuthenticatorConfig {  
  
    // 生成的key长度( Generate secret key length)  
    public static final int SECRET_SIZE = 10;  
  
    public static final String SEED = "g8GjEvTbW5oVSV7avL47357438reyhreyuryetredLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";  
    // Java实现随机数算法  
    public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";  
    // 最多可偏移的时间  
    int window_size = 3; // default 3 - max 17  
  
    /** 
     * set the windows size. This is an integer value representing the number of 
     * 30 second windows we allow The bigger the window, the more tolerant of 
     * clock skew we are. 
     *  
     * @param s 
     *            window size - must be >=1 and <=17. Other values are ignored 
     */  
    public void setWindowSize(int s) {  
        if (s >= 1 && s <= 17)  
            window_size = s;  
    }  
  
    /** 
     * Generate a random secret key. This must be saved by the server and 
     * associated with the users account to verify the code displayed by Google 
     * Authenticator. The user must register this secret on their device. 
     * 生成一个随机秘钥 
     *  
     * @return secret key 
     */  
    public static String generateSecretKey() {  
        SecureRandom sr = null;  
        try {  
            sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);  
            sr.setSeed(Base64.decodeBase64(SEED));  
            byte[] buffer = sr.generateSeed(SECRET_SIZE);  
            Base32 codec = new Base32();  
            byte[] bEncodedKey = codec.encode(buffer);  
            String encodedKey = new String(bEncodedKey);  
            return encodedKey;  
        } catch (NoSuchAlgorithmException e) {  
            // should never occur... configuration error  
        }  
        return null;  
    }  
  
    /** 
     * Return a URL that generates and displays a QR barcode. The user scans 
     * this bar code with the Google Authenticator application on their 
     * smartphone to register the auth code. They can also manually enter the 
     * secret if desired 
     *  
     * @param user 
     *            user id (e.g. fflinstone) 
     * @param host 
     *            host or system that the code is for (e.g. myapp.com) 
     * @param secret 
     *            the secret that was previously generated for this user 
     * @return the URL for the QR code to scan 
     */  
    public static String getQRBarcodeURL(String user, String host, String secret) {  
        String format = "http://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s?secret=%s";  
        return String.format(format, user, host, secret);  
    }  
  
    /** 
     * 生成一个google身份验证器，识别的字符串，只需要把该方法返回值生成二维码扫描就可以了。 
     *  
     * @param user 
     *            账号 
     * @param secret 
     *            密钥 
     * @return 
     */  
    public static String getQRBarcode(String user, String secret) {  
        String format = "otpauth://totp/%s?secret=%s";  
        return String.format(format, user, secret);  
    }  
  
    /** 
     * Check the code entered by the user to see if it is valid 验证code是否合法 
     *  
     * @param secret 
     *            The users secret. 
     * @param code 
     *            The code displayed on the users device 
     * @param t 
     *            The time in msec (System.currentTimeMillis() for example) 
     * @return 
     */  
    public boolean check_code(String secret, long code, long timeMsec) {  
        Base32 codec = new Base32();  
        byte[] decodedKey = codec.decode(secret);  
        // convert unix msec time into a 30 second "window"  
        // this is per the TOTP spec (see the RFC for details)  
        long t = (timeMsec / 1000L) / 30L;  
        // Window is used to check codes generated in the near past.  
        // You can use this value to tune how far you're willing to go.  
        for (int i = -window_size; i <= window_size; ++i) {  
            long hash;  
            try {  
                hash = verify_code(decodedKey, t + i);  
            } catch (Exception e) {  
                // Yes, this is bad form - but  
                // the exceptions thrown would be rare and a static  
                // configuration problem  
                e.printStackTrace();  
                throw new RuntimeException(e.getMessage());  
                // return false;  
            }  
            if (hash == code) {  
                return true;  
            }  
        }  
        // The validation code is invalid.  
        return false;  
    }  
  
    private static int verify_code(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {  
        byte[] data = new byte[8];  
        long value = t;  
        for (int i = 8; i-- > 0; value >>>= 8) {  
            data[i] = (byte) value;  
        }  
        SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");  
        Mac mac = Mac.getInstance("HmacSHA1");  
        mac.init(signKey);  
        byte[] hash = mac.doFinal(data);  
        int offset = hash[20 - 1] & 0xF;  
        // We're using a long because Java hasn't got unsigned int.  
        long truncatedHash = 0;  
        for (int i = 0; i < 4; ++i) {  
            truncatedHash <<= 8;  
            // We are dealing with signed bytes:  
            // we just keep the first byte.  
            truncatedHash |= (hash[offset + i] & 0xFF);  
        }  
        truncatedHash &= 0x7FFFFFFF;  
        truncatedHash %= 1000000;  
        return (int) truncatedHash;  
    }  
    /**
     * 生成谷歌身份验证数据
     * @return 
     */
	public static Map<String,Object> GoogleAuthenticator(String phone,HttpServletResponse response,String secretKey)throws ServletException, IOException 
	{
    	//生成随机密钥
    	//String secrets = GoogleAuthenticatorConfig.generateSecretKey();  
        // 把这个qrcode生成二维码，用google身份验证器扫描二维码就能添加成功  
        String qrcode = GoogleAuthenticatorConfig.getQRBarcode(phone, secretKey); 
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("qrcode", qrcode);
        map.put("secrets", secretKey);
		return map;  
	}  
}  